In managing a large telecommunications network such as the public telephone network, it is imperative that the current network status be readily available to an operator. Network status has long been displayed as tables of numerical data on video display terminals. Often, these displays are color-coded according to the status indicated by the data values. By paging over many such displays, a network manager can ascertain the status of the managed network. However, tabular displays require time and effort for a user to gather all the information needed to assess the overall status of a large network. By the time the user has gathered sufficient information, some of it will be out of date, so this situation assessment may be faulty. Because of the delay, control responses by the user may be late and incorrect.
More recently, systems have used computer graphics to display geographic maps of the managed network, with network elements and links color-coded according to the status. Map displays show an array of network elements, but are arranged geographically. Unfortunately, such displays necessarily have very low information density.
Using the public telephone network as an example, Switches are scattered non-homogeneously across a service area, and they are usually very highly connected. On a typical map display, connections between only about ten nodes can be shown simultaneously before some lines become impossible to resolve from each other. Although individual switches can be collapsed into a hierarchy of abstract "cluster" nodes, the upper limit of instantaneously displayed complexity is still about 10 nodes and their links, resulting in the other links and nodes being ignored.
The underlying reason that map displays are so information-poor when applied to network management is that they are constrained to be faithful to a geographic structure that is applicable to only a few network problems. Only the network's topological structure is useful for the vast majority of network problems. Hence, a map is inefficient at showing information relevant to network problems. Moreover, because the map is faithful to a questionable structure, it is rarely helpful and often misleading in diagnosing problems.
Using either the conventional tabular or the map approach, the following practical implications result:
Smaller parts of the network must be managed by an individual, thus requiring a larger workforce. PA1 Fewer network problems can be efficiently detected and handled. Thus it is likely that more errors will be made, compromising the quality of service delivered by the network.
Thus it is desirable that network status can be displayed in such a way that the user can observe the overall performance of a very large network and, from the same display, perceive sufficient detail to diagnose network malfunctions.